The increasing cost of fossil fuels has a substantial impact on the residential sector, business of all types and industry in general. Accounting for the costs of energy has become a major and pressing issue throughout developed society, and it is more vexing than ever before. The long term outlook for fossil fuels provides bases for little or no expectation of major downturns in fuel costs. Conservation, alternative energy sources, and changes in life style and manner of doing business are all being more widely and seriously considered in attempts to address the challenges of the energy situation.
Transportation is a key element of the propagation of energy costs throughout society. Goods require movement from one place to another to facilitate manufacturing and distribution of products to consumers. In the case of perishable goods, such as fresh and frozen foods, the large and increasing costs are not only due to the energy required for moving the goods around but also the energy required for keeping the goods cool or frozen during transport. Businesses engaged in the storage and transportation of perishable foods face then a double impact as fuel costs rise, and their customers likewise share the cost.
Refrigerated transport of perishable foods, frozen or chilled foods in particular, generally involves the utilization of tractor-trailer trucks operating on highways. Food is loaded from storage sites into insulated portions of trailers where required refrigeration is maintained typically by a dedicated gasoline or diesel engine powered refrigeration system that is on-board the trailer. As the tractor-trailer moves the load from one point to another, generally stopping at various points to make deliveries, the on-board refrigeration system maintains the required cold conditions in the trailer. The fuel required to operate such on-board refrigeration systems is a significant portion of the fuel usage in refrigerated transport of foods.
While one or more on-board dedicated engines provides stand-alone refrigeration for the trailer or refrigerated compartment, the fuel conversion efficiency of the typical engine appropriately sized for this service is less than the efficiency, for example, of the large tractor engine that provides motive power for the tractor-trailer. Moreover, energy recovery such as is practicable with regenerative braking offers a source of energy that might be useful in meeting some of the energy demands of refrigerated food transport. Likewise, alternatives, such a solar energy collection may offer other sources.
Driver comfort and convenience is also a significant factor in such transport activities. For example, cab air conditioning and heating must be maintained not only during cruising speeds, but often while stopped and parked for relatively short periods. When a sleeper cab is in use, maintaining cab cooling and heating is important for operator rest. While keeping such systems active can be done by keeping the tractor engine running or idling, this is a very inefficient mode of operation. Such engines, while relatively efficient at cruising speeds, can be relatively inefficient at low speeds such as at idle. An alternative that has found significant use to address this problem is the so-called auxiliary power unit, or APU. One typical APU includes a battery pack with an inverter to produce AC power to power an APU cab air condition system (HVAC system) that is used to air condition the cab when the tractor engine is not operating at an efficient speed. This type of APU also includes a charger system for charging the battery pack from shore power when available. Other types of APUs may include a small dedicated internal combustion engine to power the APU AC system.
A common configuration for a tractor-refrigerated trailer rig might include, in addition to the tractor engine, a refrigeration unit engine. Additionally, there may be alternative sources of recovered or available energy or power such as regenerative braking systems and solar collection systems. While every energy or power source has a particular principal consumer—locomotion for the tractor engine and refrigeration for the refrigeration engine, for example—there may be conditions in which energy or power may be channeled or used in different ways in order to achieve optimal efficiency of each power or energy source and reduce overall fuel consumption.
There is a need for a system and approach for management of the various power or energy sources in refrigerated transport for optimal energy efficiency.